This invention relates to circuit breakers. More particularly, this invention relates to a draw out air circuit breaker assembly having a telescopic racking handle.
Generally, an air circuit breaker includes mechanical operating components that are mainly exposed to the environment. The air circuit breaker includes a main contact which is either opened to interrupt a path for electrical power traveling from an electrical power source to a load or closed to provide a path for the power to travel from the source to the load and disposed in a plastic housing. Arc chambers are disposed in the said housing are used for extinguishing an arc generated while opening and closing the contacts. The draw out type air breaker is movable to be separated from the power source and the load circuit in order to facilitate maintenance.
The draw out air circuit breaker includes a racking handle for racking the circuit breaker into and out of a breaker cassette. The racking handle is utilized for racking the circuit breaker into the breaker cassette and is then stored. There are several disadvantages associated with the conventional racking handle of the draw out air circuit breakers. One disadvantage is that the storage space in the breaker cassette for the racking handle is limited due to interference with other moving or stationary parts. Another disadvantage is that it is difficult to rack higher ampere rated frames using the conventional racking handle due to the number of primary disconnect contacts increasing with ampere rating, and the external force required to be applied during a rack-in operation. Thus, it would be desirable to have a racking handle which can be easily stored upon racking the circuit breaker and which includes a larger mechanical advantage to enable ease in racking higher frames.